## The First Six Books: Together with the Eleventh and Twelfth |

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Page 18

Ax . In BD take any point F , and from AE , the greater , cut off AG equal to AF , the lefs , and

Ax . In BD take any point F , and from AE , the greater , cut off AG equal to AF , the lefs , and

**join**FC , GB . A Because AF is equal to AG , and AB to AC , the two fides FA , AC are equal to the two GA , AB , each to each ; and they ... Page 19

I. qual to AC , the lefs , and

I. qual to AC , the lefs , and

**join**DC ; there- fore , because in the triangles DBC , ACB , DB is equal to AC , and BC common to both , the two fides DB , BC are equal to the two AC , CB , each to each ; and the angle DBC is equal to ... Page 21

1 . qual to AD ;

1 . qual to AD ;

**join**DE , and upon it de- fcribe an equilateral triangle DEF ; then**join**AF ; the ftraight line AF bifects the angle BAC . Becaufe AD is equal to AE , and AF is common to the two triangles DAF , EAF ; the two fides DA ... Page 22

F Take any point D in AC , and a make CE equal to CD , and upon DE describe the equila- teral triangle DFE , and

F Take any point D in AC , and a make CE equal to CD , and upon DE describe the equila- teral triangle DFE , and

**join**FC ; the ftraight line FC drawn from the given point C is at right angles to the given ftraight line AB . Page 23

Poft . meeting AB in F , G ; and bi- A F G B D fect FG in H , and

Poft . meeting AB in F , G ; and bi- A F G B D fect FG in H , and

**join**CF , C IO . I. CH , CG ; the ftraight line CH , drawn from the given point C , is perpendicular to the given ftraight line AB . с ...### What people are saying - Write a review

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### Common terms and phrases

added alfo alſo altitude angle ABC angle BAC bafe baſe becauſe bifected Book Book XI centre circle circle ABCD circumference common cone cylinder defcribed definition demonftrated diameter divided double draw drawn equal equal angles equiangular equimultiples excefs fame fame multiple fecond fegment fhall fides fimilar firft folid folid angle fore four fourth fquare fquare of AC ftraight line given angle given in fpecies given in pofition given magnitude given ratio greater Greek half join lefs magnitude meet oppofite parallel parallelogram perpendicular plane prifms produced PROP propofition proportionals pyramid rectangle rectangle contained remaining right angles Take taken thefe THEOR theſe third triangle ABC wherefore whole

### Popular passages

Page 474 - The circumference of every circle is supposed to be divided into 360 equal parts, called degrees ; and each degree into 60 equal parts, called minutes ; and each minute into 60 equal parts, called seconds ; and these into thirds, &c.

Page 170 - If two triangles have one angle of the one equal to one angle of the other and the sides about these equal angles proportional, the triangles are similar.

Page 81 - THE straight line drawn at right angles to the diameter of a circle, from the extremity of...

Page 105 - DEF are likewise equal (13. i.) to two right angles ; therefore the angles AKB, AMB are equal to the angles DEG, DEF, of which AKB is equal to DEG ; wherefore the remaining angle AMB is equal to the remaining angle DEF.

Page 167 - AC the same multiple of AD, that AB is of the part which is to be cut off from it : join BC, and draw DE parallel to it : then AE is the part required to be cut off.

Page 10 - When a straight line standing on another straight line makes the adjacent angles equal to one another, each of the angles is called a right angle; and the straight line which stands on the other is called a perpendicular to it.

Page 62 - AB be the given straight line ; it is required to divide it into two parts, so that the rectangle contained by the whole, and one of the parts, shall be equal to the square of the other part.

Page 112 - To describe an equilateral and equiangular pentagon about a given circle. • Let ABCDE be the given circle; it is required to describe an equilateral and equiangular pentagon about the circle ABCDE. Let the angles of a pentagon, inscribed in the circle...

Page 200 - If two triangles have two angles of the one equal to two angles of the other, each to each, and one side equal to one side, viz. either the sides adjacent to the equal...

Page 38 - F, which is the common vertex of the triangles ; that is, together with four right angles. Therefore all the angles of the figure, together with four right angles, are equal to twice as many right angles as the figure has sides.